IEEE 802.11 Task Group (TG) ah (referred to herein as IEEE 802.11 TGah or simply TGah) accepted a concept of restricted access window (RAW) operation. An access point (AP) allocates a medium access interval called RAW for a group of stations (STAs) within a beacon interval and broadcast this information using a (Short) Beacon frame. Within a (short) beacon frame, RAW allocation information is indicated in a RAW parameter set (RPS) element. This restricts channel access to a small number of STAs and spreads their access attempts over a much longer period of time. It also improves the efficiency of the utilization of the medium by reducing collisions. Further, it increases fairness by assigning restricted channel access windows to different groups of STAs.
IEEE 802.11 TGah also accepted a concept of periodic resource allocation, named as a periodic restricted access window (periodic RAW or PRAW). The AP may also indicate the presence of a PRAW allocation by setting the periodic RAW indication subfield to 1 in the RAW control subfield of RAW Assignment field in the RPS element. A STA that receives the RPS element with the PRAW indication subfield set to one in the RAW control subfield of RAW Assignment field obtains information of RAW periodicity in the PRAW periodicity subfield. The periodicity of RAW assignment for a group of STAs indicated in the RAW group subfield of the RAW assignment field of RPS element is valid for a fixed number of periods indicated in the PRAW validity subfield of the periodic operation parameters subfield in the RAW assignment field of RPS element.